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    <title>Document</title>
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    <!-- 平方数之和 -->
    <script>
      var judgeSquareSum = function (c) {
        let l = 0,
          r = Math.floor(Math.sqrt(c)),
          t
        while (l <= r) {
          t = l * l + r * r
          if (t === c) return true
          else t < c ? l++ : r--
        }
        return false
      }
      console.log(judgeSquareSum(5))
    </script>
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</html>
